I was playing with Migration using the Migration Extras Profile2 example. To register the the example, I have to click the Register button on /admin/content/migrate/registration. The following log error occured:
MigrateException: Failure to sort migration list - most likely due to circular dependencies involving OgMigrateContent,OgMigrateUser,OgUiMigrateAddField,OgUiSetRoles in migrate_migrations() (line 80 of E:\Robert\My Documents\MyWork\drupaldesigns.dev\public_html\sites\all\modules\migrate\migrate.module).
The only way to get the Migration UI working again is to delete the entries in the migrate_status database table.
I then simply disabled the Profile2 migration example, and clicked the Register button again. OG is the only module in my install that is using Migration.
This issue makes it impossible to Register other migration modules.